A major clinical issue in the treatment of schizophrenia is that substance use is associated with increases in psychosis, relapse, and rehospitalization. Whether this association is due to symptom exacerbation following substance use or to substance use as a self-initiated coping strategy for dealing with symptoms of illness is less clear. Some evidence, both self-report and type of substance used, suggests the latter may be true for a large percent of substance using schizophrenics. The purpose of this study is to determine if substance use follows an increase in clients' and case managers' ratings of clients' generic and idiosyncratic symptoms of illness. It is hypothesized that specific classes of substances will be used following specific symptom clusters. Case managers of 100 subjects from a Community Support Program of a Mental Health Center with a diagnosis of schizophrenia and thought to be using drugs and or alcohol will monitor their clients' symptoms, compliance with prescribed medication, and substance use weekly for 12 weeks. Concurrent with their case managers monitoring, 30 of the 100 subjects will monitor daily for 12 weeks their symptoms, compliance with prescribed medication and substance use. Ratings of negative symptoms will be done on all 100 subjects and social functioning assessed on the subsample of 30 subjects so that the relationship of these variables with substance use can be explored. A time series analysis will be performed to test the major hypotheses. Findings from the study will be used to determine if any substance use constitutes abuse and if interventions to facilitate symptom relief other than substance use are needed.